You are on a jury, the facts and evidence are being presented and it's your job to weigh all of that information and make a judgement on the defendant's guilt. Most people could do this objectively and not let personal biases influence their decisions, right?Wrong. There is a double whammy when you're a black defendant in the American justice system. We have known for a long time that black Americans are far more likely to be convicted than their white counterparts, and given harsher prison sentences when found guilty (see Three Worst Jury Verdicts).

Thanks to a team of Yale researchers, we now know that the criminal justice system is likely to be influenced by other negative stereotypes too. In the study, mock jurors were presented with a case of cheque fraud. The defendant was identified from one of four photographs (the experimental condition): large female, slim female, large man or slim man.

There was no fat bias when men and women were evaluating the guilt of the male defendants, and no fat bias emerged when female participants were judging the female defendants. But male jurors were significantly more likely to exhibit a fat bias when assessing the guilt or innocence of the female defendants. Males were more likely to judge fat women as being more likely to be guilty of cheque fraud on the basis of the same evidence, than the slimmer defendant.

But wait, it gets worse ... Slim male participants were the worst of all. Not only were they much more likely to find the obese woman defendant guilty, they were more likely to ascribe the obese woman defendants as being 'repeat offenders' and 'having more awareness of their crimes'.

As you explore the IB Psychology learning outcome: 'Explain the formation of stereotypes and their effect on behaviour', you will come to learn that that these negative stereotypes are activated automatically and below the level of conscious thought. They are also very, very difficult to overcome. Crash diet if you're a woman facing jury trial in America?